#include <iostream>
using namespace std;
int n, l, r; unsigned long long a[1569];
int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(false);
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> l >> r;
		bool found = false;
		for (int j = r >> 6; j < 1563 && !found; j++) {
			if (a[j] == 0) continue;
			for (int k = 0; k < 64; k++) {
				if ((a[j] & (1ULL << k)) && (j << 6) + k >= r) {
					a[j] -= 1ULL << k;
					found = true;
					break;
				}
			}
		}
		if (r - l < 64) {
			for (int j = r - 1; j >= l; j--) {
				if (a[j >> 6] & (1ULL << (j & 63))) a[(j + 1) >> 6] |= 1ULL << ((j + 1) & 63), a[j >> 6] -= 1ULL << (j & 63);
			}
		}
		else {
			r++; l++;
			for (int j = (r & 63); j >= 1; j--) {
				if (a[r >> 6] & (1ULL << (j - 1))) {
					a[r >> 6] -= 1ULL << (j - 1);
					a[r >> 6] |= 1ULL << j;
				}
			}
			if (a[(r >> 6) - 1] & (1ULL << 63)) {
				a[(r >> 6) - 1] -= 1ULL << 63;
				a[r >> 6]++;
			}
			for (int j = (r >> 6) - 1; j > (l >> 6); j--) {
				a[j] <<= 1;
				if (a[j - 1] & (1ULL << 63)) {
					a[j - 1] -= 1ULL << 63;
					a[j]++;
				}
			}
			for (int j = 63; j >= (l & 63 ? (l & 63) : 1); j--) {
				if (a[l >> 6] & (1ULL << (j - 1))) {
					a[l >> 6] -= 1ULL << (j - 1);
					a[l >> 6] |= 1ULL << j;
				}
			}
			if ((l & 63) == 0 && a[(l >> 6) - 1] & (1ULL << 63)) {
				a[(l >> 6) - 1] -= 1ULL << 63;
				a[l >> 6]++;
			}
			l--;
		}
		a[l >> 6] |= 1ULL << (l & 63);
	}
	int ret = 0;
	for (int i = 0; i < 1563; i++) {
		for (int j = 0; j < 64; j++) {
			if (a[i] & (1ULL << j)) ret++;
		}
	}
	cout << ret << '\n';
	return 0;
}